Triplefins: Little Fishes Seldom
Seen – and a small lesson in biogeographyby Wouter Holleman

Species of three of the six
families of blennioid fishes occur in South African waters: true blennies
(Family Blenniidae), klipfishes (Clinidae) and triplefins (Tripterygiidae).

Triplefins are found in all
temperate and tropical waters of the world. They are easily identified
by their three dorsal fins, from which they derive their name,
Tripterygiidae, based on the Genus Tripterygion (from tri,
three, and pterygion, a fin). They are, however, seldom seen
because they are generally small, cryptically coloured, benthic (bottom)
dwellers which live amongst algae and anything else attached to rocks,
under ledges, and in every nook and cranny imaginable.

There are more than a hundred
species of triplefins worldwide, with about 23 species in the Western Indian
Ocean, of which 11 occur in South African waters, and of these, eight species
can be said to be East Coast inhabitants, bearing in mind, of course, that
our knowledge of the diversity and distribution of our marine fishes is
far from perfect. In other words, there may well be unrecorded or
undescribed species along our coast, particularly in deeper waters.

As one moves from temperate
to tropical areas, the species composition of the ichthyofauna changes
and species diversity increases. Also, more ‘isolated’ areas
– and that is a relative term – are more likely to have ‘endemic’
species, which are confined to a particular geographic area and do not
occur elsewhere. South African triplefins illustrate these points
quite nicely.

The temperate southern Cape
coast, from a little north of East London, where the tropical fish fauna
becomes more apparent, to about the Orange River mouth on the west coast,
can be considered an ‘isolated’ area. There are about 88 endemic
species of fishes, including three triplefins, along this south coast area.

The barrier that forms the boundary
of this isolated south coast area is the warmer tropical waters of the
inshore KwaZulu-Natal habitats.

The Cape triplefin, Cremnochorites
capensis, is known from False Bay to Coffee Bay. It grows to
about 120 mm, is rough and scaly and banded grey in colour with bits of
rusty-orange. It is found fairly commonly in sub-tidal rocky gullies
down to about 30 m.Cremnochorites capensis,
70 mm.

Two new species, Acanthanectes
hystrix and Acanthanectes rufus were described by myself
and Colin Buxton in 1993 from collections made in 10 to 24 m at Port Elizabeth
and the Tsitsikamma National Park. A new genus, Acanthanectes
(from acanth, a thorn or spine, and nektes, a swimmer); was
created for these species, because these two species have several
little
spinelets on each side of the dorsal-fin spines and also on the subopercle
bones.

Acanthanectes hystrix
(hystrix is the Latin name for a porcupine) is similar to Cremnochorites
capensis, with 4 or 5 conspicuous, irregular, dark bars on the body
and 4 spines in the first dorsal fin.Dorsal-fin spines from
Acanthanectes species.

Acanthanectes hystrix,
37 mm.

Acanthanectes rufus,
is pale orange-red, with 5 or 6 narrow, palebars on the upper part of the
body. It was also found at Port Alfred.Acanthanectes rufus,
42 mm.These three south coast
endemic triplefins have not been collected north of Port Alfred.

Moving north of East London,
we find the hotlips triplefin, Helcogramma obtusirostre, abundant
in weedy tide pools and on shallow reefs from the Transkei to the Red Sea,
across the Indian Ocean and into the Western Pacific. It grows to
about 45 mm. Adult males are dark brown to black, with scarlet on
the head and first dorsal fin and crimson and neon blue on the lips and
pectoral-fin base.Helcogramma obtusirostre,
male, 43 mm.

It has been suggested
that the very dark males are in full breeding dress and may have a ‘harem’
of females. This is not uncommon amongst reef fishes. The dark
colouration, particularly a dark or black head is quite common for male
triplefins.

The female hotlips is, by
contrast, drab, mottled and blotched with cream and brown.Helcogramma obtusirostre,
female, 41 mm.Little is known about the
behaviour of these small fishes, and some interesting observations could
be made by a keen and patient Fish-Watcher who is prepared to lie quietly
in a warm tide pool with mask and snorkel to see what they get up to.

At Coffee Bay and northwards
we find a second Helcogramma species, the blackfin triplefin, H.
fuscopinna, with dark fins (fuscus, dark or dusky, and pinna,
fin) and a brilliant neon-blue line from upper lip, below eye and
onto opercle (gill cover). It is one of a complex of species found
all the way to Melanesia in the Western Pacific.

Helcogramma fuscopinna,
48 mm.

In tidepools and diving
on reefs in KwaZulu-Natal, you will encounter six more triplefin
species. The rough-head triplefin,
Norfolkia brachylepis (Schultz) resembles Cremnochorites capensis
(banded grey and russet, with 4 spines in the first dorsal fin), but it
is smaller and more slender, and the tentacle on top of the eye is simple
or crenulate (orbital tentacle branched in Cremnochorites).Norfolkia brachylepis,
55 mm.

N. brachylepis occurs
from Aliwal Shoal northwards, and is also widely distributed
in the Indo-West Pacific area. Norfolkia springeri (the name
used in Smiths’ Sea Fishes) is a junior synonym of this species.

The five species of the genus
Enneapterygius along our east coast are usually less than 30 mm
and highly cryptic. They all live sub-tidally, but may also
be found in tidepools.

The yellow triplefin, Enneapterygius
abeli, is bright yellow, and males have a black head. It is found
from Aliwal Shoal north to the Red Sea and widely in the Indian Ocean.Enneapterygius abeli,
28 mm.

The blotched triplefin,
E. ventermaculus, is mottled orange-brown and light green; the underside
of the head and pelvic fins white, and there is a row of 4 black spots
on the anal fin base. It is endemic to the Western Indian Ocean
from Aliwal Shoal to Pakistan.Enneapterygius ventermaculus,
female, 29 mm (above), male, 31 mm (below).

At Sodwana Bay, we find three
additional species of Enneapterygius: the multicoloured E.
pusillus, the barred triplefin, E. clarkae, and an as yet unnamed
species, which was collected a few years ago near Kosi Bay on a flat,
current-swept reef at 35 metres.

The multicoloured ‘high-crest
triplefin’,
Enneapterygius. pusillus, has the first dorsal fin distinctly
higher than the second dorsal fin; the pelvic fins are black, and the second
dorsal and anal fins are dusky. It occurs from Sodwana Bay to the
Red Sea.Enneapterygius pusillus,
31 mm.

The barred triplefin, Enneapterygius
clarkae, has 4 or 5 dark bars on the body, the last at the base of
the tail fin and a row of 5 or 6 dark spots along the anal-fin base.
Known from Sodwana Bay, but not common in our area; also
in Red Sea and at islands in Western Indian Ocean.Enneapterygius clarkae,
28 mm.

Let us recap briefly.
Three species of triplefin are endemic to the southern Cape coast.
On the east coast, north of East London, we find Helcogramma obtusirostre
and H. fuscopinna. In the Umkomaas area of KwaZulu-Natal,
there are an addtional three species in two genera; and eight species
of triplefin are known from Sodwana Bay.

This illustrates quite neatly
endemicity in geographically ‘isolated’ areas, the change in species composition
as one moves from cooler to warmer waters, and the increase in species
diversity as one moves towards the tropics.